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Your wasting your money on a $600 radiator, the Ebay ones for $239 work great.
If your car came with a 3 core then put one back because the top support is different than a 4 core.
Best bet is go to Autozone and order one that is close to original and it will work fine for years.

 

There are a few good options. I have seen the 2 core Ebay rads for a bit more than $200. Griffin has their US made A/G body Dominator series rad with big dual 1.25" cores for under $400 in automatic from Summit. I am getting the F body version for my G body in manual trans for under $300. The A/G body rad is 2" too wide to fit my car, not sure why they say G body. The Ebay aluminum rads cool fair at best, I had a Champion 3 core and ran 190 with a 160 high flow thermostat on my 7.9 to 1 350. It ran more like 210 with my 8 to 1 403. I expect the Griffin to cool much better. More cores is not better but bigger tube size is the difference maker.

 

You must have had problems somewhere else because with an Ebay radiator I can't get it to heat up enough.

 

Two different motors? The G body has less air flow possibly but I say it is no great rad for cooling. Nice construction for the Champion. I have a leaking two core aluminum that out cooled it.

 

And more cooling fins per inch as that is where the heat is transferred to the air.

 

I think we need some more information before jumping into a new radiator purchase as there are other things that affect the cooling system.

Do you have a real temperature gauge on it? If so, what is it reading? We need to know how "hot" is "hot".
Also, what is the outside air temp?

What type of fan do you have - with or without fan clutch? You need to make sure the fan is pulling sufficient air across the radiator.

Do you have a shroud? This is also important for proper air flow.

For reference, I have no overheating issues during 115+ ºF summer temps with a fairly stock cooling system, and I doubt many folks out there are driving around in anything close to this kind of heat.

 

OK, a new radiator it is, then. Be aware than new is not always better as some new radiators have fewer tubes per row and fewer cooling fins-per-inch, so the new radiator doesn't have the cooling capacity of the old radiator. Check the specs and ask what others have used to help you get a radiator that will do the job properly.

 

put this in my 70 Supreme last year:

Summit 380457 3 core alum radiator with trans cooler – stock fan & shroud

radiatorACfanshroud_zpsd2f6d2a0.jpg

Works great and not too bad on the price ($300). If I run a 160* thermostat it won't go over that, same with a 180*. That's on the hottest summer day with the AC on and driving the car hard. Had to adjust the bottom mounts a little and "massage" the stock 3 core top. Nothing major.

Will work perfect for your set up.

 

I wish I had written down the part number, but I used an aluminum radiator from a "P" series van, $100 new that worked great in my Skylark. Not a bolt in, but almost.